• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 63 subscribers
  • Views 615 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ25601: bq25601 charge principle analysis

shaonianlang
Prodigy 50 points
Part Number: BQ25601

Recently, I have being studying the charge principle of bq25601, but i cannot analysis what's the MOSFET Q1 Q2 Q3,and Q4 state when the chip provides constant current or constant volltage for our battery,

Espcially, when we provide small charge current(when battery's voltage below 3V), how does the chip ensure the SYS pin output between 3.6V and 4.5V for our load?

Here is the link for bq25601 technical referrence:  www.ti.com/.../bq25601.pdf.

and the intenal function structure is at page 16, Could someone help me solve this problems?

Thanks for replies!!

Best Regards!

  • 0
    TI__Prodigy 150 points
    Hi,

    Q1 is the reverse blocking FET. It is there to provide protection against current leaving the device through VBUS, if boost mode is not enabled.

    When the battery voltage is below the system voltage, the converter controller will switch Q2 and Q3 so that the system voltage is greater than VSYSMIN. VSYSMIN, by default, is set to 3.5V, but it can be changed by changing REG01[1:3]. When the battery voltage is below the system voltage, Q4 operates in linear mode (LDO mode). Control loops in the charger maintain the system voltage is above VSYSMIN, and the charge current is controlled by the gate drive for Q4.

    When the battery voltage is at or above VSYSMIN, then the Q4 turns completely on, and the voltage between SYS and BAT is the charge current multiplied by the RDSON of Q4. This applies when the charger is charging in constant current and when the charger is charging in constant voltage.

    I hope this helps!

    Bill